Conference Agenda

The nascent field of silicon core fibres is attracting increased interest as a means to exploit the excellent optical and optoelectronic functionality of the semiconductor material directly within the fibre geometry. Compared to their planar counterparts, this new class of waveguide retains many advantageous properties of the fibre platforms such as flexibility, cylindrical symmetry, and long waveguide lengths. Furthermore, owing to the robust glass cladding it is also possible to employ standard fibre post-processing procedures to tailor the waveguide dimensions and reduce the optical losses over a broad wavelength range, of particular use for nonlinear applications. This presentation will review progress in the development of nonlinear devices from the silicon core fibre platform and outline exciting future prospects for the field.

Miles Padgett and Simon Mekhail, The University of Glasgow

Endoscopic imaging systems based upon bundles of optical fibres are commonplace across medical and industrial applications. However, even just one of these optical fibres, less that 100µm in diameter, transmits enough spatial modes to relay an entire image, but intermodal dispersion rephases the output modes such that any input image becomes unrecognisable at the output. This problem can be overcome by measuring the transmission matrix of the fibre and using the inverse of the matrix to set the required input light fields to produce a scanning spot over the scene at the output. The backscattered light from this spot can then be measured to create an image of the scene. A current limitation is that the matrix is time consuming to measure and the required input beams time-consuming to calculate. Furthermore, each time the fibre is moved the matrix needs to be remeasured and the input beam recalculated. Here we show that the use of high-speed cameras and GPU computing can reduce this measurement and calculation time to a few 10s seconds, inspiring new modes of operation. When combined with the use of graded index fibres to minimises the sensitivity of the matrix to movement of the fibre, we show that 5-10 rapidly pre-recorded matrices are sufficient to create an imaging system that works over a wide range of fibre positions, giving near continuous imaging from a compact instrument. Such ultra-minimally invasive imaging systems have many uses in inspection and medical applications.

Emerging healthcare needs, including global healthcare, personalized medicine, and point-of-care applications are demanding breakthrough advancements in diagnostic and bioanalytical tools. Towards this goal, our lab is developing next-generation nanophotonic lab-on-a-chip systems offering high performance in accuracy, response time, integration, throughput, and affordability while reducing complexity, cost and device footprint. We build optical biosensors, spectroscopy, bioimaging and microarray technologies to sensitively detect and analyze biological samples, including disease biomarkers, misfolded protein aggregates, nucleic acids, drugs, and living cells. To achieve our objectives we uniquely combine nanophotonics with advanced nanofabrication, microfluidics, surface chemistry, and data science techniques. In particular, we engineer optical metasurfaces exploiting plasmonics and dielectric resonators to fundamentally increase interaction of light with nanometric sized biomolecules. In this talk, I will present some of our recent works on surface enhanced mid-infrared spectroscopy such as an AI-aided optofluidic biosensor capable of differentiating misfolded disease proteins and high-Q gradient metasurfaces for ultra-broadband operation as well as describe nanophotonic single-cell and organoid microarrays that can enable high-throughput monitoring of extracellular secretion for screening applications.

In this talk I will describe the use of a range of advanced photonics-based approaches of light sheet microscopy and digital holographic microscopy for label-free imaging. A driver for this work is the understanding of the development of the pre-implantation mammalian embryo [1-4] and improve IVF outcomes.

Embryo quality is a crucial factor affecting live birth outcomes. However, an accurate diagnostic for embryo quality remains elusive in the IVF clinic. Exploiting advanced optical imaging can assess the embryo in 3D and determine its metabolic rate and other physical parameters. This may ultimately prove to be a new multimodal diagnostic approach for embryo health.

Cellular metabolism is a key regulator of energetics, cell growth, regeneration, and homeostasis. The endogenous metabolic cofactors, nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) and flavin adenine dinucleotide (FAD) can be imaged through their autofluorescence. By performing this with hyperspectral imaging at subcellular resolution may assist in determining embryo viability in a clinical setting. Such hyperspectral imaging can be used to determine the ploidy status of the embryo [1]. By using new implementations of light sheet imaging, we can extend this imaging to 3D [2]. Separately, we can tailor digital holographic microscopy (DHM) to measure spatio-temporal changes in refractive index during the development of the embryo that are reflective of its lipid content. Accumulation of intracellular lipid is known to compromise embryo health thus making this a further useful approach for diagnosis [3]. Overall, advanced photonics adds useful, label-free multimodal information for IVF success and can be gentle enough to not effect viability [4].

[1] T. C. Y. Tan et al., Hum. Reprod. 37(1), 14–29 (2021).

[2] Josephine Morizet et al., ACS Photonics 10, 4177-4187 (2023)

[3] George O. Dwapanyin et al., Biomed. Opt. Express 14, 3327-3342 (2023)

[4] C. A. Campugan et al., J. Assist. Reprod. Genet. 39(8), 1825–1837 (2022)

Nonlinear and disordered photonic systems exhibit intricate dynamics, encompassing extreme events like rogue waves and non-trivial statistical behaviors. Remarkably, the application of spin-glass theory provides a fitting theoretical framework to elucidate the complexities inherent in these nonlinear optical systems. Experiments involving disordered lasers and nonlinear optical propagation have unveiled direct evidence of Replica Symmetry-Breaking transitions, a pivotal prediction of the spin-glass theory that had eluded confirmation for decades.
While spin-glass theory has found prominence in modern machine learning, combinatorial optimizations, and artificial intelligence, its interdisciplinary connections with photonic systems present a compelling opportunity. We explore the potential to harness these connections to develop innovative non von Neumann devices tailored for large-scale computing.
An introductory review of photonic spin glasses theory and experiments is presented alongside new findings that pave the way toward a new generation of computing devices demonstrating superior scalability compared to existing quantum annealers and Ising machines.

References

1. N. Ghofraniha, et al., Experimental evidence of replica symmetry breaking in random lasers, Nature Communications 6, 6058 (2015)

2. D. Pierangeli, et al., Large-scale photonic Ising machine by spatial light modulation, Phys. Rev. Lett. 122, 213902 (2019)

3. M. Calvanse Strinati, et al., Hyperscaling in the coherent hyperspin machine, Phys. Rev. Lett. 132 (2024)

In this talk I will present the backward optical parametric oscillator (BWOPO), a new nonlinear device which have some unique properties. It is a single chip, quasi-phase matched, nanodomain-engineered crystal which, when pumped with an intense laser beam, generates a narrow-linewidth, frequency-stable, contra-directional down-converted beam, and a collinear beam that inherits the spectrum of the pump. Compared to regular optical parametric oscillator the BWOPO provides a very narrow spectrum, easily tunable without mode hops and with a high conversion efficiency. It is among other things excellently suited for differential absorption lidar (DIAL) spectroscopy. I will describe the BWOPO properties in details and how it can be used.

Traditional workflow in surgical pathology involves multiple labor-intensive steps, such as tissue removal, fixation, embedding, sectioning, staining, and microscopic examination, which are time-consuming, costly, and require skilled technicians. Intraoperative tumor assessment (ITA) necessitates faster histological evaluation for real-time surgical guidance, typically using frozen section (FS) technique with hematoxylin and eosin (H&E) staining. However, an FS biopsy often comes with certain limitations, such as half-an-hour turnaround time, freezing artifacts, and potential tissue loss. To overcome these limitations, virtual H&E imaging modalities have been developed over the years aiming for rapid tissue imaging with microscopic details. However, such modalities often differ from the gold standard H&E characteristic appearance, primarily because of incorporating non-H&E contrast mechanisms, thus affecting diagnostic accuracy and applicability

In this talk, I will present True-H&E rapid fresh pathology, an innovative approach leveraging third-harmonic and two-photon signals from H and E dyes to produce optically-sectioned 2D images in fresh whole-mount tissues. Our method, invaluable for intraoperative tumor prognosis, eliminates the artifacts due to freezing, physical sectioning, and non-H&E staining, enabling pathologists to distinguish normal and tumor tissues without requiring special training., while meeting the whole-slide-imaging standard and enhancing the speed, safety, and accuracy.